With the increasing use of household electrical appliances, people demand that receptacles installed in their houses be capable of protecting them from serious injury when accidentally touched or other ground fault conditions occur. Thus, ground fault circuit interrupters are designed to break the electrical continuity upon detecting a ground fault condition occurring at an alternating current (AC) load.
Many electrical wiring devices including receptacles have a line side that is connectable to an electrical power supply, and a load side that is connectable to one or more loads and at least one conductive path between the line side and load side. When a person accidentally comes in contact with the line side of the AC load and an earth ground at the same time, a serious injury may occur because the human body forms another conductive path for the electrical current to flow through. There is a strong desire for electrical wiring devices that can break electric power supply to various loads such as household appliances and consumer electronic products.
The GFCI devices can detect a ground fault condition and break the electric power supply by employing a sensing transformer to detect an imbalance between the currents flowing in the phase (also known as “hot”) and neutral conductive paths of the power supply. A ground fault condition happens when the current is diverted to the ground through another path such as a human body, that results in an imbalance between the currents flowing in the phase and neutral conductors. Upon detection of a ground fault condition, a breaker within the GFCI devices is immediately tripped to interrupt the electrical continuity and removes all power supply to the loads.
Some circuit interrupters, such as GFCI receptacles, have a user accessible load in addition to the line side and load side connections. Users can connect other household appliances to the power supply through plug entries on the receptacle. However, due to the similarity of line side and load side terminals, instances may occur where the line wires are connected to the load side connection and the load wires are connected to the line side connection. This is known as reverse wiring. When reverse wiring occurs, the GFCI devices usually do not provide ground fault protection to the user accessible load. It is a problem if there is no warning provided to an installer when the GFCI devices have reverse wiring. Thus, it is desired to design a GFCI device which can disable the reset function when the GFCI device has reverse wiring. Moreover, it is strongly desired that a GFCI does not even provide electricity to user accessible loads to better protect consumers when there is reverse wiring.
In addition, because of the high stability requirement of the GFCI devices' quality, it is also desired for GFCI devices to have a simpler design, less components so that they are easier to be assembled, installed, and correctly wired.